This invention relates to an information recording system for use in a magnetic tape system which permits storing and searching of image information.
Recently, there have been developments in image information storing and searching systems. These systems can store visual image information obtained from documents through two-dimensional optical scanning. The system additionally permits a desired portion of the stored image information to be searched and subsequently reproduced for recording or displaying. In large-capacity image information memorizing systems, the use of magnetic tape has been proposed as the storage medium.
In such magnetic tape systems an endless magnetic tape is employed having a plurality of parallel recording tracks extending in the direction of its rotational movement. More particularly, a magnetic head is moved in a direction at right angles to the direction of movement of the magnetic tape to thereby form a plurality of parallel recording tracks. Thus, a plurality of tracks can be used serially. For example, when recording document information, the document is fed page by page, image information (i.e., video signals) for each page is successively read and written as unit image information on the recording track. As shown in the prior art structure of FIG. 1, image information for the first page is recorded on frame number "1" of a first recording track of magnetic tape 23. A tape mark 26 establishes a reference position on magnetic tape 23 for frame number "1". The second page is recorded on frame number "2" adjacent to that of frame number "1" with an adequate space provided therebetween. Likewise, successive information for third (i.e., frame number "3"), fourth (i.e., frame number "4") and subsequent pages are successively recorded on the tape in the order of the pages read.
In the magnetic tape shown in FIG. 1, the endless magnetic tape is driven one complete excursion in about 7 seconds (e.g., the tape has a length of 36 m and is moved at a speed of 5 m/sec). Approximately 2 seconds is needed for reading one page of information from a document by optical scanning. The image information which has been read is stored in a buffer memory, and then recorded onto the magnetic tape. The period required for this recording is extremely short compared to the time period necessary to read information from the document due to high recording density and high tape speed. As a result, after recording the first unit of image information from the first page at the first frame position on the tape (i.e., frame number "1"), it is necessary to wait until the tape completes substantially one excursion from that position, so that the recording head will then come into position at the second frame position (i.e., frame number "2") to commence recording the next page or unit of image information from the document. This means that only one page or unit of information can be recorded with a single complete excursion of the tape; consequently, the recording efficiency is extremely low.